Return mechanism for stopwatches



Ju y 1970 NAOKI TAKASHINA 3,51

RETURN MECHANISM FDR STOPWATCHES Filed July 1, 1968 2 Sheets-Sheet 1 FIG./

hl O I '1, 23 3 3 "5 Q L w July 7, 1970 v NAOKITAKASHINA 3,513,826

RETURN MECHANISM FOR STQPWATCHES I Filed July 1. 19 68 2 Sheets-Sheet 2 United States Patent Oflice Patented July 7, 1970 3,518,826 RETURN MECHANISM FOR STOPWATCHES Naoki Takashina, Tokyo, Japan, assignor to Kabushiki Kaisha Daini Seikosha Filed July 1, 1968, Ser. No. 741,595 Claims priority, application Japan, Aug. 21, 1967, 42/515,301 Int. Cl. G04f 7/04 US. Cl. 58-74 2 Claims ABSTRACT OF THE DISCLOSURE A return mechanism for stopwatches including a hammer pivotaly mounted on the base of said stopwatch and formed with acting surfaces adapted to operatively engage the minute heart and second heart respectively and means for displacing the point of pivotable mounting of the hammer along the base plate so that said hammer acting surfaces will operatively engage both the minute and second hearts at the zero position thereof.

BACKGROUND OF THE INVENTION This invention relates generally to the return mechanism of stopwatches. The return of both the minute and second hands of a stopwatch to zero is accomplished by means of a hammer provided with two acting surfaces which operatively engage a minute heart and a second heart respectively set on the minute hand arbor and the second hand arbor. However, minor errors in each part of the mechanism inevitably result in a small interstice between one of the acting surfaces of the hammer and the face of either the minute heart or second heart. This results in the failure of either the minute or second hands to precisely return to the zero position. The known method of correcting the aforedescribed condition consists of filing down the acting surface in contact with one of the two hearts until both acting surfaces are in contact with their respective heart cam. However, such filing enlarges the coefficient of friction of the acting surface to prevent the return to zero of the corresponding hand or results in the rounding of the acting surface to extend the dead point range. These defects require much time and skill to correct. By providing means for displacing the point of pivotal mounting of the hammer along the base plate of the stopwatch, the return mechanism can be readily adjusted so that the hammer acting surfaces will operatively engage both the minute and second hearts at the zero position thereof without otherwise adversely affecting the accuracy of the return mechanism.

SUMMARY OF THE INVENTION Generaly speaking, in accordance with the invention, a return mechanism for stopwatches having a hammer pivotally mounted on the base plate of said stopwatch and formed with acting surfaces adapted to operatively engage the minute heart and second heart respectively, is provided with means for displacing the point of pivotable mounting of said hammer along said base plate so that said hammer acting surfaces will operatively engage both said minute and second hearts at the zero position thereof. The displacing means preferably comprises two spaced pins extending from the base plate and an adjusting plate having the hammer pivotably mounted thereon and having a plurality of sets of correspondingly spaced apertures formed therein, each of said sets of apertures being adapted to receive the pins therein to firmly maintain the adjusting plate relative to the base plate. In a second embodiment according to the invention, the adjusting plate upon which the hammer is pivotably mounted is formed with at least two uniformly spaced internal cam surfaces adapted to engage spaced pins upstanding from the base plate to firmly maintain the adjusting plate relative to said base plate in a plurality of positions.

A third embodiment of the invention consists of an adjusting plate pivotably mounted on the base plate, the hammer being pivotably mounted on said adjusting plate at a point spaced from the point of pivotable mounting of said adjusting plate, and means for fixing the adjusting plate is a plurality of positions about the point of pivotal mounting thereof.

Accordingly, it is an object of this invention to provide means for adjusting the return mechanism for stopwatches so that the acting surfaces of the hammer will operatively engage both the minute and second hearts at the zero position thereof.

Another object of the invention is to provide a return mechanism for stopwatches which is readily adjustable without requiring filing of the acting surfaces of the hammer.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.

The invention accordingly comprises the features of construction, combinations of elements, and arrangements of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a plan view of the first embodiment;

FIG. .2 is a cross-section of the principal part of the first embodiment;

FIG. 3 is a plan view of the principal part of the first embodiment;

FIG. 4 is a plan view of the principal part of the second embodiment;

FIG. 5 is a plan view of the principal part of the third embodiment; and

FIG. 6 is a cross-section of the principal part of the third embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIGS. 1-3, wherein the embodiment according to the invention is shown. The hammer 1 is provided with two acting surfaces 2 and 3, a projection 4 which touches projection 21 of the operating lever 18, an aperture 5 and a projection 7 which is pressed by a spring 13 and is turned clockwise under the action of said spring. The minute heart 10, operatively engaged by the acting surface 2, is carried on the minute hand arbor 9 and the second heart 12, operatively engaged by the acting surface 3, is carried on the second hand arbor 11. During driving, a projection 8 touches a pillar wheel (not shown in the drawings) to check the turning of this hammer, but also the hammer to turn clockwise due to the turning of said pillar wheel when both the minute and second hands stand still.

The adjusting plate 14 is, at the center, provided with a pivot 15 which holds said hammer 1 by a hole 6 and is provided with apertures or setting holes A-A', B-B', CC', and D-D which face each other respectively. The space between the setting holes comprising each set of facing setting holes is equally to that between the two supporting pins 16 and 16' upstanding from the base plate 17. Naming the center of the pivot 15 as P, segments of a line are a 3 and each difference is of the 7 two pins 16 and 16 serve as supports for the adjusting plate 14 to firmly maintain said adjusting plate relative to base plate 17 when the pins are receivedwithin one of the sets of setting holes A-A, B-B', C-C' and D-D'.

Operating lever 18 is fitted on pivot 19 of base plate 17 and is provided with an operating face 20 and a projection 22 which is pressed by the spring 23, the action of which turns lever 18 couterclockwise.

Normally, projection 21 of the operating lever 18 is located within aperture of hammer 1 and is maintained therein by the action of .the spring 23 to prevent hammer 1 from turning clockwise due to the action of spring 13. Acting surfaces 2 and 3 are out of the turning locus of minute heart and second heart 12 respectively.

As in known stopwatches, upon pushing a starting button (not shown in the drawings) both minute and second had arbors 9 and 11 begin to turn. Upon pushing said starting button again, both arbors stop, the minute and second hand indicating the elapsed time. (Since this is the mechanism outlined inthe known Stopwatches, a detailed description thereof is not included herein.) Next, after measuring, operating face of operating lever 18 is pushed to return both minute and second hand to zero. At this time, as operating lever 18 turns clockwise against spring 23 and propection 21 of the operating lever 18 is removed from aperture 5 of hammer 1, hammer 1 is released and turns clockwise about the pivot 15 of the adjusting plate 14 under the action of the spring 13, and acting surfaces 2 and 3 touch the minute heart 10 and the second heart 12 respectively, returning them to the zero position and thereby returning the minute hand on the arbor 9 and the second hand on the arbor 11 exactly to zero.

It is usually impossible for both acting surfaces of the hammer to contact fully with both second and minutes heart cams, because each part has errors in its shape or dimensions, and the accumulation of such errors inevitably causes a slight clearance between one of the two heart cams and the respective acting surface of the hammer. But it is important that the acting surface of the second heart cam fully contact against said cam so that the second hand is brought back exactly to zero. 1

According to the invention, any slight clearance between the heart cam and the hammer is easily correctable by providing emans for displacing the point of pivotal mounting of hammer 1 along base plate 17.

In the first embodiment, as shown in FIGS. 1-3, the adjusting plate 14 is so positioned that one of the sets of setting holes AA, B-B', C-C', D-D thereof is fitted to the pins 16 and 16' of the base plate 17, to receive said pins therein to firmly maintain and support said adjusting plate relative to said base plate. The point of pivotable mounting of hammer 1 may be displaced by removing said adjusting plate so that another of said sets of setting holes is fitted to said pins.

In the second embodiment, as shown in FIG. 4, instead of several pairs of setting holes formed in adjusting plate 14, said adjusting plate is formed with two uniformly spaced cam surfaces 24 and 25 which define a plurality of sets of center points E-E','F-F', G-G', H-H' and I-I which are adapted to receive pins 16 and 16' upstanding from 'base plate 17. When adjusting plate 14 is so positioned that one of said sets of center points is fitted to said pins, said adjusting plate is firmly maintained and supported relative to base plate 17. As'in the case of the first embodiment, the point of pivotable mounting 15 of hammer 1 may be displaced by removing adjusting plate 14 and fitting another of said sets of center points to said pins.

In the third embodiment of the innvention, as shown in FIGS. 5 and 6, the adjusting plate 14 is provided with a setting hole 26 and an arcuate slot 27 uniformly spaced along its length from setting hole 16. The pivot 15 is located between said setting hole and slot. Setting hole 26 isfitted to a supporting pin 16 upstanding from base plate 17. The point of pivotable mounting of hammer 1 may be displaced by pivoting the adjusting plate 14 about support pin 16. After adjustment, means are provided for fastening the adjusting plate 14 to base plate 17 such as screw 16 which extends-through slot 27 to said base plate.

The return mechanism forstopwatches according to the invention oifers substantial advantages over the known arrangements in that it permits,' by means of a simple adjustment, the elimination of .any clearance between the operating surfaces of the hammer and the respective second and minute heart cams at their zero positions. Further, despite the ease of adjustment, the adjusting plate, having the hamer pivotably mountedthereon, is very securely fastened to the base plate, so that the adjustment is not disturbed despite the pressure of the various springs.

It will thus be seen that the objects set forth above, and those made apparent from the preceding description, are efiiciently attained and, since certain changes may be made in the above constructions without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover'all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as a matter of language, might be said to'fall therebetween.

What is claimed is:

1. In combination with a return mechanism for stopwatches having a hammer pivotably mounted on the base plate of said stopwatch and formed with acting surfaces adapted to respectively operatively engage the minute heart and second heart set on a minute hand arbor and a second hand arbor, respectively, the improvement which comprises means for displacing the point of pivotable mounting of said hammer along said base plate so that said hammer acting surfaces will operatively engage both said minute andsecond hearts at the zero position thereof, said displacing means comprising at least two spaced pins upstanding from said base plate and an adjusting plate having a plurality of sets of corresponding spaced apertures therein, each of said sets of apertures being adapted to receive said pins therein to firmly maintain said adjusting plate relative to said base plate, said hammer being pivotably mounted on said adjusting plate, whereby the point of pivotable mounting of said hammer is displaced along said base plate when said adjusting plate disposed so that said pins received in one of said sets of apertures, is moved so that said pins are received in another of said sets of apertures.

2. In combination with a return mechanism for stopwatches having a hammer pivotably mounted on the base plate of said stopwatch and formed with acting surfaces adapted to respectively operatively engage the minute heart and second heart set on a minute hand arbor and a second hand arbor, respectively, the improvement which comprises means for displacing the point of pivotable mounting of said hammer along said base plate so that said hammer acting surfaces will operatively engage both said minute and second hearts at the zero position thereof, said displacing means comprising at least two spaced pins upstanding from said base plate and an adjusting plate having said hammer pivotably mounted thereon'and having at least two internal cam surfaces formed therein, said cam surfaces being spaced and adapted to receive and retain said pins therebetween at each of a plurality of distinct positions to maintain said adjusting plate relative to said base plate, whereby the point of pivotable mounting of said hammer is displaced along said base plate when said adjusting plate, disposed so that said pins received by said internal cam 6 surfaces at one of said positions, is moved so that said 271,999 11/1950 Switzerland. pins are recived in another of said positions. 279,962 12/1951 Switzerland.

285,850 9/1952 Switzerland. References Cited FOREIGN PATENTS RICHARD 5 B. WILKINSON, Primary Examiner 1,003,141 2/1957 Germany.

G. 'H. MILLER, JR., Assistant Examiner 

